In the past, a vehicle-mounted radar apparatus derives a position of a target with respect to a vehicle (radar apparatus) by transmitting a transmission wave from a transmitter antenna and receiving a reflection wave from the target by a receiver antenna. The detailed process thereof is as follows. A signal processing unit of the radar apparatus generates a beat signal by mixing a transmitting signal corresponding to the transmission wave of which a frequency is changed in a given period, and a receiving signal corresponding to the reflection wave. That is, the signal processing unit generates the beat signal based on a frequency difference (beat frequency) between the transmitting signal and the receiving signal in each period including an up period in which the frequency ascends in a predetermined period, and a down period in which the frequency descends in a predetermined period.
Then, the signal processing unit generates a signal (transformed signal) for every frequency by processing the beat signal through FFT (Fast Fourier Transform). Among the transformed signals, a signal exceeding a threshold of a predetermined signal level is extracted as a peak signal. The signal processing unit derives paired data by pairing the peak signal of the up period and the peak signal of the down period based on a given condition.
For example, the signal processing unit derives paired data (predicted paired data) predicting the current paired data based on the paired data which is derived in the past, and derives a peak signal (predicted peak signal) predicting the current peak signal. And, the signal processing unit extracts a peak signal (predicted peak signal) predicting the current peak signal from the predicted paired data. And, the signal processing unit extracts the current peak signal included in a predetermined range, with a frequency of the predicted peak signal being as a base point, as a current peak signal corresponding to the predicted peak signal, for every up period and down period. The signal processing unit derives paired data by pairing the peak signal of each corresponding period from the frequency of the extracted peak signal and the angular information.
The signal processing unit derives a distance (vertical distance) from the vehicle to the target, or a distance (horizontal distance) of the target with respect to a vehicle running in a direction substantially perpendicular to a traveling direction of the vehicle. Further, the signal processing unit derives a relative speed of the target with respect to the vehicle. The signal processing unit outputs determined information about the target, including the position of the target and the relative speed of the target, to a vehicle control device, so that the vehicle control device performs necessary vehicle control according to the target information.
But, if the derived target is a stationary object (e.g., road sign of a cantilever type or gate type installed above the road, or illumination installed at ceiling of tunnel) installed at a position sufficiently higher than a vehicular height of the vehicle, such a target is a target which is not required for the control of the vehicle. Information about the target is removed not to be output to the vehicle control device. For example, there are Patent Documents 1 and 2.
Patent Document 1: Japanese Patent Application Publication No. 2001-324566A
Patent Document 2: Japanese Patent Application Publication No. 2007-093481A
However, for example, in the case of the tunnel having the low ceiling, the target information corresponding to the illumination or the like installed at the ceiling may be misjudged as a target of the preceding vehicle. Specifically, in the tunnel having the low ceiling so that a passenger car can drive, but a vehicle having a high vehicular height, such as a truck or a bus, cannot drive, the height of the illumination or the like installed at the ceiling is possibly set to be lower than the height of the truck or bus. In this instance, it is misjudged as the preceding vehicle despite the target corresponding to the illumination or the like of the ceiling, and thus the target information is not removed and is output to the vehicle control device, so that the vehicle control device performs the vehicle control of the brake or the like.